As a new type of Ti—Si zeolite molecular sieve, ETS-10 is a crystal with a three-dimensional porous structure having a 12-membered ring formed by SiO4 tetrahedron connected with TiO6 octahedron through oxygen bridges. It can be directly used for various catalytic reaction due to its unique skeleton structure and element composition. However, since a microporous ETS-10 has smaller pore size (0.74 nm), it may impede a reactant having larger molecules from entering the micropores when the molecular size of the reactant is larger than the pore size of the micropore, which is unfavorable for the catalytic transformation of the macromolecular reactants, thus limiting its production and application in industry. One way to solve this problem is to introduce mesopores into the grains of the microporous zeolite ETS-10.
Claudiu et al. (Chemical Communications, 2006, 882-884; Journal of Catalysis, 2008, 254, 84-90) proposed to treat microporous zeolite ETS-10 with microwave irradiation in an aqueous hydrogen peroxide solution to produce a mesoporous structure therein, which is, however, will destroy the skeleton structure of the microporous ETS-10 with a limited amount of mesopores as introduced.
Tang Tiandi et al. (ChemCatChem. 2015, 521-525, ZL 2014104060.X) reported that a mesoporous zeolite ETS-10 was successfully synthesized by using N,N-diethyl-N-octadecyl-N-(3-methoxysilylpropyl) ammonium bromide as a soft templating agent. Although this method has been greatly improved with regard to the post-treatment technology, it still needs a step of calcining at high temperature to remove the templating agent, which will cause environmental pollution; moreover, many templating agents are expensive, which is unfavorable for the extensive production and application.
Xiaojun Ni et al. (Direct synthesis of mesoporous zeolite ETS-10 and Ni-ETS-10 with good catalytic performance in the Knoevenagel reaction, J Porous Mater, 2016, No. 23, pp. 423-429) disclosed a method for synthesizing a mesoporous zeolite ETS-10 and zeolite Ni-ETS-10, wherein the mesoporous ETS-10 is synthesized by a Ti—Si gel having a molar composition of 4.4 Na2O/1.9 K2O/1.0 TiO2/7.1 SiO2/0.65 MRC/163.0 H2O through hydrothermal crystallization. In this method, the mesoporous zeolite ETS-10 containing a metal can only be synthezised under the interaction of a mesoporous templating agent MRC and a metal source.
It is found that there are no any existing techniques in which zeolite ETS-10 with high mesopore volume can be synthesized without a templating agent.